60 THE AMINO ACIDS 



observations of Embden and Knoop that any doubt 

 of Neumeister's view was entertained. In experiments 

 designed to show the fate of proteoses and peptones 

 when brought into contact with the intestinal wall 

 Embden and Knoop were able to show the presence in 

 the blood of substances having the properties of pro- 

 teoses and peptones. They held that the mucous mem- 

 brane of the intestine neither synthesized these sub- 

 stances to a larger molecule, as for example to a coagu- 

 lable protein, nor were they hydrolyzed to the amino 

 acid stage but, on the contrary, absorption took place 

 directly. The results of Embden and Knoop were con- 

 firmed by some observers and discredited by others. 

 Schumm for example was always unable to find a trace 

 of proteose in the blood both under normal and ab- 

 normal conditions of health. Abderhalden and his co- 

 workers maintained that the substances giving 

 reactions for proteoses and peptones were present 

 because of imperfect methods employed in the separa- 

 tion of the coagulable protein from the blood. 



It has been pointed out by others, however, that there 

 is a possibility of the presence in the blood of a protein 

 naturally non-coagulable which would still give the 

 reaction the biuret test significant under the experi- 

 mental conditions for the presence of proteose or pep- 

 tone. Zanetti described such a protein in the blood 

 and found that it belonged to the group of mucoids. 

 Among others, Howell believes in the existence in the 

 blood of a protein possessing some of the character- 

 istics of the proteoses and peptones, for example, non- 



